Electron discharge device



Nov. 25, 1958 C. F. MILLER ELECTRON DISCHARGE DEVICE Filed Oct. 22. 1954 WITNESSES'I mvsmon Carl F. Miller.

ATTORNEY United States Patent ELECTRON DISCHARGE DEVICE Carl F. Miller, Bath, N. Y., assignor to Westinghouse Electric Corporation, East Pittsburgh, Pa., a corporation of Pennsylvania Application October 22, 1954, Serial No. 463,937

6 Claims. (Cl. 313-250) This invention relates to electric discharge devices and more particularly to improvements in the electrode assembly.

It is an object of this invention to provide an improved electrode assembly for an electric discharge device.

In the manufacture of electron discharge devices in the vacuum tube industry, the component parts of the electrode assembly are fabricated on separate pieces of machinery or equipment and then treated in various ways to clean or coat the component parts and then assembled by manual means. The assembly of the component parts of the electrode assembly by manual means entails 'large expense for manual labor and a large shrinkage results due to the human element. The shrinkage problem has further been enhanced by the fact that the size of the component parts and the distance therebetween have steadily decreased.

It is accordingly another object of this invention to provide an improved electrode assembly suitable for automatic assembly.

It is another object to provide an improved electrodeassembly which is particularly suited to a tube requiring high values of transconductance.

It is another object to provide an electric discharge device which facilitates the mass production of tubes having uniform values of transconductance.

It is another object to provide an electric discharge device in that the electrode assembly may be fitted together without incurring distortion in the elements due to the problems associated with automatic assembly techniques and machinery. 7

It is another object to provide an electric discharge device in which the design of the electrode assembly is such that it does not require extreme accuracy in placement of the elements in the assembly procedure.

These and other objects are effected by my invention as will be apparent from the following description taken in accordance with the accompanying drawing, in which:

Figure 1 is a sectional view of an electric discharge device embodying my invention;

Fig. 2 is a cross-sectional view of Fig. 1 taken along the line II-II of Fig. 1;

Fig. 3 is a greatly enlarged view of a portion of a space element with a cathode and control grid positioned thereon; and

Fig. 4 is a plan view of another type electrode structure that may be used embodying my invention.

Referring in detail to Figs. 1, 2 and 3, there is shown an electric discharge device embodying my invention in a preferred form. The device or tube shown is a pentode type vacuum tube and is similar to the double or duplex type pentode and consists of a cathode, two half grid control grids, two half grid screen grids, two half grip suppressor grids and two half'anode elements.

The tube is comprised of an envelope of suitable type and of a material such as glass with an electrode assembly 12 enclosed therein. The envelope 10 shown is 2,862,134 Patented Nov. 25, 1958 of conventional design and includes a tipped-off exhaust tube 14 on the top of the envelope and a button stem header 16 closing 01f the bottom portion of the envelope. A plurality of metal stems or lead-ins 17-23 are sealed through the header 16 and are welded to the elements of the electrode structure 12 within the envelope 10. The lead-in elements 17-23 not only supply the neces-- sary voltage to the elements of the electrode assembly 12 but support the same.

In the tube illustrated the electrode assembly 12 includes an electron-emissive element or cathode 24 of the indirectly heated type. The cathode 24 comprises in general a tubular metallic sleeve 26 having a rectangular cross section. Electron emissive coatings 29 and 30 are placed on the two opposite sides of the rectangular sleeve 26 having the larger dimensions and flanges 32 located on the upper and lower ends of the tubular metallic member 26. The cathode sleeve 26 is connected by suitable means to the lead-in wire 21. A filament heater 33 of suitable type is positioned within the tubular sleeve 26 of the cathode 24 and electrically insulated therefrom so as to provide heat for the emissive surfaces 29 and 30. The ends of the filament heater 33 are connected to the lead-in wires 19 and 20.

Positioned adjacent to the cathode sleeve 26 and parallel to the emissive coated sides 29 and 30 are the respective control grids 41 and 42 in the form of half grid members. Each of the control grids 41 and 42 are of similar planar type elements and consists of a frame 43 of sheet-like material in a specific embodiment rectangular which supports and positions the active portion 45 of the grid 41 or 42. The active portion 45 consists of lateral wires or a mesh structure across the opening in the rectangular frame member 43. The opening in the frame 43 is of similar dimensions to the electron-emissive surface 29 or 30 adjacent thereto. The active section 45. of the grid 41 or 42 which is comprised of the lateral wires is attached by suitable means such as a notching and peening or brazing to one side of the frame member 43. The two control grids 41 and 42 are connected together by'a suitable connecting means 46. It has also been found advantageous to place a rib or corrugation 44 in the vertical portion of the support frame 43 to increase the strength of the grids 41 and 42. It has also been found advantageous to provide extensions 47 on both the bottom and top of the vertical portions to aid in the mounting assembly. The lead-in member 22 is connected to the lower right extension 47 of the control grid 41.

Positioned adjacent to the control grids 41 and 42 and also in the form of half grid members are the screen or shield grids 51 and 52. The shield grids 51 and 52 are also positioned substantially parallel to the control grids 41 and 42 and on the remote side of the respective control grids 41 and 42 with respect to the electron-emissive surfaces 29 and 30 of the cathode sleeve 26. The shield or screen grids 51 and 52 are also of the planar type members of like construction and similar in construction to that of the control grids 41 and 42. The dimensions of the frame 53 and the opening therein are both slightly greater than the same element on the control grids 41 and 42. Since it is desirable that the exterior portion 54 of the frames 53 be positioned substantially at uniform distances from other grid members, two bends may be made in the vertical portions of the frame member 53 so that the plane of the active grid portion 55 is closer to the control grid 41 or 42 than is the exterior portion 54 of the vertical portion of the frame 53. A rib 56 may also be made in the exterior portion 54 of the frame support 53 to give greater strength to the member in a similar manner as the control grid. The screen grids 51 and 52 which are also half grids are connected together electrically by the conductive means 56. The screen grids 51 and 52 are connected to the exterior of the envelope by means of the lead-in member 18.

Positioned adjacent to the screen or shield grids 51 and 52 are suppressor grids 61 and 62' which'are also 'in the form of halfgrid members. The suppressor grids "61 and 62 are also similar in structure to the control 'grids 41 and 42 and are substantially parallel to the screen grids 51 and 52'and positioned on the remote sides thereof with respect to'the control grids 41 and 42. The exterior dimensions of the frame support 63 and the active portion 65 of the grid 61 or 62 are of'slightly greater dimensions than that of the screen grids'51 and 52. The suppressor grids 61 and 62 are connected together electrically by means of the. conductive'means 66. The suppressor grids 61 and 62 are connected to the exterior of the envelope by meansof the lead-in 17.

Positioned adjacent to the suppressor grids'"61'and' 62 on the remote side thereof with, respectto'the screen grids 51 and 52 are two half type anode members 71 and 72 which are also planar in structure and comprising a solid sheet '75 of suitable material of dimensionscomparable with the active portion of the suppressor grid members 61 and 62 and in line therewith. Theplate or active portion 75 of the anode 71 or 72 hasa plurality of cars 74 positioned thereon and in thespecific embodiment the ears are positioned on portions on the vertical sides of the sheet member 75 at the upper and lower corners with a rivet on downturned portion 76-on the exterior portion of the ears 74. The two half'anodes 71 and 72 are also connected together by means of a conductive member 77. The anodes 71 and 72 are connected to the exterior of the envelope 10 by means of the lead-in member 23 which is connected to the lower right-hand rivet portion 76 of the anode car 74.

For the purpose of spacing the electrode elements within the electrode assembly 12, a lower and upper pairof spacer elements 81, 82, 83 and 84 are provided. The spacer elements 81, 82, 83 and 84 are all similar in structure and a description will be limited to the-lower pair of spacer elements 81 and 82. The spacer elements 81 and 82 lie within one plane transverse to the plane of the electrodes and are generally a sheet of insulating material such as mica or ceramic in the form of a sector of a circle. By utilizing this type of configuration, the curved portion 85 of the sector is adjacent to the tube envelope 10 and therefore aids in securing a greater stability of mounting of the electrode assembly 12 within the envelope 10. The tapered portions orsides 86 and 87 of the spacers 81 and 82 which may be termed the opposing edges of the spacer elements 81 and 82 are positioned so that the electrode elements are retained between the opposing edges 86 and 87 of the two spacer elements 81 and 82. Located substantially at the point where the tapered edges 86 and 87 meet, and centrally located with respect to the opposing edges, is a projection 88 which is rectangular in shape and having a notch 89'.located substantially at the center of the exterior portion of the projection. The cathode sleeve 26 is retained in position within the electrode asembly by placing the flanges 32 of the sleeve 26 within the notch 89 of the projections 88 on the two spacer elements 81 and 82. At the foot of the projection 88 is located a notch 90 into the on-positioning edges 86 and 87 of the spacer element, and into which the control grids 41 and 42 are positioned. The control grids 41 and 42 as thus mounted abut against the edges of the projection 88 and are retained in this abutting position by means ofthe notches 90. The space between the electron-emissive surfaces 29 and 30 of the cathode sleeve 26 and'the control grids 41 and 42 is very critical and in some tubes is of the order of .002 inch. This spacing is important in that thetransconductance of the tube is determined .primarily by this spacing. By the utilization of the structure thus-described, the spacing of the cathode 24and the control grids 41-and 42'is determined by thespacer elements 81 and82, andamoreuniw form production of tubes is obtained. From the notches 90 located at the foot of the projection 88, the opposing edges 86 and 87 taper back in a step relationship. At the foot of the next riser 92 of the step portion 91 is located another notch 93 into which the shield grids 51 and 52 are positioned, and the riser at the bottom of 95 of the next step 94 is located another notch 96 into which the suppressor grids 61 and 62 are positioned and retained. The mica spacers 81 and 82 are held or pressed against the exterior portions of the electrode elements by means of the half plate members 71 and 72, which have the rivet portions 76 of the extending ears 44 passing a through openings within the mica spacers 81 and 82 and are riveted thereto so as to obtain a strong durable electrode assembly.

In the method of assembly of the device described in Figs. 1, 2 and 3, the structure as previously described lends itself to automatic assembly. Thernica spacers tioned into the electrode assembly by suitable mechanical means along a horizontal plane that is parallel to the electromemissive surface of the cathode, or the electrodes may be inserted along a vertical plane perpendicular to the plane of the emissive surfaces of' the cathode. The spacers'may then be moved in so that the opposing edges clamp all of the grid electrodes, and the cathode in fixed position as shown in detail in Fig. 1 of the drawing. The anode halves may thenbe brought into position and-their rivet portion inserted into the openings in the mica spacers and riveted theretoso as to complete the electrode assembly, which may be inserted intothe envelope and processed in a well known manner.

The mica spacers described with reference to Figs. 1, 2 and 3 were symmetrical with respect to the section line II'II, the notches and steps of like dimensions on both sides of the projection. In Fig. 4, I have shown an embodiment which lends itself even more so to the automatic assembly technique. In this figure, the mica spacers 98 and 99 are not symmetrical about the line 100, but instead are such that the planar grid members 104, 105 and 106 maybe dropped into the top half 101 above line 100 of the mica spacers 98 and '99, the cathode 103 having previously been inserted as in Fig. 1, and the mica spacer maybe moved in a slight distance so as to retain the planar grids within the top portion of the mica spacers. This is the position'shown in Fig. 4. The electrode assembly may then be turned over so that the lower portion 102 of the mica spacers 98 and 99 will be in-position so that the planar grids 107, 108 and 109 may be dropped into the electrode assembly. The notches in the lower portion 102 of the mica spacers 98 and 99 are of less depth than the notches in the top portion 101 of the mica spacers 98 and 99, and the distance between the diametrically opposed stepped portions in the lower portion'102 is greater than the distance between corresponding steps in the upper portion 101. The distance between the bottom of diametrically opposed notches in upper section.101 is the same as corresponding notches in the lower section 102. Thus, the electrodes 107, 108 and 109 may be dropped into position and the spacers moved in towards each other was to lock all planar elements Within the mica spacers 98 and 99. The mica spacers 918'and'99 may then be fastened by the insertion of the anode members as described with reference to Figs. 1, 2 and 3.

While I have shown my invention in only two forms, it will be obvious to those skilled in the art that it is not so limited, but. is susceptible of various other changes and modifications Without departing from the spirit and scope thereof.

. 1 claim as my invention: v 1. 'An electric discharge device comprising an envelope having an electrode assembly therein, said electrode assembly having a plurality of planar type electrodes, means positioning said electrodes within said assembly comprising a pair of spacers of insulating material lying within a plane transverse to the planes of said planar type electrodes, said spacers fixed in relationship with respect to each other, said electrodes positioned between opposing edges of said spacers, and the spacing between said opposing edges progressively varying along their length, said opposing edges of said spacers having a plurality of notches therein in which said planar electrodes are seated and thereby positioned with respect to each other.

2. An electric discharge device comprising an envelope having an electrode assembly therein, said electrode assembly having a plurality of planar type electrodes, means positioning said electrodes Within said assembly comprising a pair of spacers of insulating material lying within a plane transverse to the planes of said planar type electrodes, said spacers fixed in relationship with respect to each other, said electrodes positioned between opposing edges of said spacers, said opposing edges of said spacers inclined with respect to each other and having a plurality of notches therein diametrically opposite, said electrodes seated within said notches and thereby positioned with respect to each other.

3. An electric discharge device comprising an envelope having an electrode assembly therein, said electrode assembly having a plurality of planar type electrodes, means positioning said electrodes within said assembly comprising a pair of spacers of insulating material lying within a plane transverse to the planes of said planar type electrodes, said spacers fixed in relationship with respect to each other, said electrodes positioned between opposing edges of said spacers, said opposing edges of said spacers having a centrally located projecting portion diametrically opposite with respect to each other with a notch therein and said opposing edges tapering away from said central portion with respect to the other opposing edge, said electrode seated Within said notches and thereby positioned with respect to each other.

4. An electric discharge device comprising an envelope having an electrode assembly therein, said electrode assembly having a plurality of planar type electrodes, means positioning said electrodes within said assembly comprising a pair of sheets of insulating material lying within a plane transverse to the planes of said planar type electrodes, said sheets fixed in relationship with respect to each other, said electrodes positioned between opposing edges of said sheets, said opposing edges of said sheet having a plurality of stepped portions therein and a notch positioned at the foot of the riser of each of said stepped portions, said electrodes seated within said notches and thereby positioned with respect to each other.

5. An electric discharge device comprising an envelope having an electrode assembly therein, said electrode assembly having a plurality of planar type electrodes, means positioning said electrodes within said assembly comprising a pair of sheets of insulating material lying within a plane transverse to the planes of said planar type electrodes, said sheets fixed in relationship with respect to each other, said electrodes positioned between opposing edges of said sheets, opposing edges of said sheet having a plurality of diametrically opposite stepped portions with notches positioned at the foot of the riser of each of said stepped portions and the exterior planar electrodes having means attached for retaining said sheets in said fixed position, said electrode seated within said notches and thereby positioned with respect to each other. 6. An electric discharge device comprising an envelope having an electrode assembly therein, said electrode assembly having a plurality of planar type electrodes, including a rectangular indirectly heated cathode with separate emissive surfaces on two sides of said rectangular cathode and flanges located on the other two sides of said member, planar grid electrodes with a mesh section and surrounding supporting frame and two planar type anodes with connecting ears thereon; means positioning and retaining said electrodes comprising a pair of sheets of insulating material within a plane transverse to the planes of said planar type electrodes, said sheets provided with apertures through which said anode ears may pass so as to retain said sheets in a fixed position with respect to each other and said anode member, means fixing the position of said cathode and said grids with respect to said anodes comprising a centrally located projection positioned on each of the opposing edges of said sheets, said projection having a notch therein and adapted to receive the flange of said cathode, so that one of said emissive surfaces of said cathode will face only one anode and are parallel to and equally spaced from their respective anode, said sheets provided with notches on the opposing edges adjacent to each side of said projection so that said grid members will abut against the sides of said projection and be retained in position with respect to said cathode by said notches to position said grids at equal distances from each of said emissive surfaces.

References Cited in the file of this patent UNITED STATES PATENTS 1,238,660 Field-Frank Aug. 28, 1917 1,672,233 Skinner June 5, 1928 1,974,086 Smith Sept. 18, 1934 2,012,038 Eitel et al. Aug. 20, 1935 2,091,047 Kaufeldt Aug. 24, 1937 2,166,744 Seelen et 'al July 18, 1939 2,212,643 Koros et al Aug. 27, 1940 

